Method and apparatus for treating liquids

ABSTRACT

A method and apparatus for treating fluids by transmitting ultrasonic energy into the fluids to produce high intensity cavitations in the fluids as the fluids pass through the apparatus. The fluids are retained in the apparatus for a sufficient period of time to destroy contaminates in the fluids, neutralize acids or bases in the fluids and dissociate other chemical compounds.

This is a divisional of application Ser. No. 09/755,915, now U.S. Pat.No. 6,547,935, filed Jan. 6, 2001.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for treating fluids andparticularly for treating water to destroy contaminates in the water andsterilize the water. The apparatus and method are effective to treat thewater using ultrasonic energy to dissociate compounds in the water.

BACKGROUND OF THE INVENTION

The use of ultrasound to treat various materials is well known to thoseskilled in the art. The general principles relating to the use ofultrasonic energy to treat various materials and its ability to resultin dissociation of materials and to perform other difficult chemicalreactions and the like is discussed in “The Chemical Effects ofUltrasound”, Kenneth S. Suslick, Scientific American, February 1989,pages 80–86.

Ultrasound has been used for a number of applications and ultrasonictransducers are well known to those skilled in the art and arecommercially available. Some applications of ultrasonic techniques areshown in U.S. Pat. No. 4,164,978 issued Aug. 21, 1979 to Harold W.Scott; U.S. Pat. No. 4,169,503 issued Oct. 2, 1979 to Harold W. Scott;and U.S. Pat. No. 5,951,456 issued Sep. 14, 1999 to Harold W. Scott.These patents are hereby incorporated in their entirety by reference.

The availability of pure fluids is an ongoing problem in our society. Inmany instances it is desirable to be able to purify various gases whichmay contain bacterial or viral contaminates or various gaseous compoundcontaminates. The purification of gases, while it is frequentlyrequired, is less frequently required than the purification of liquids.Liquids, such as water, are widely used for a variety of purposes.Techniques for purifying water range from ionization techniques, todistillation and the wide variety of techniques used in municipal andother water treating plants to produce potable water. All of thesetechniques are relatively expensive and require extensive processequipment and process activity and expense to purify the water.Accordingly, improved and more efficient methods have long been soughtfor purifying fluids and particularly for purifying liquids such aswater.

SUMMARY OF THE INVENTION

According to the present invention an apparatus for treating fluids isprovided. The apparatus comprises a radial ultrasonic transducer havingan inner surface, a central passageway having a central axis, a tubehaving an outer surface and centrally positioned at least partiallythrough the central passageway, a fluid inlet to the passageway, and afluid outlet from the passageway.

The present invention further comprises a method for treating a fluidwherein the method comprises passing the fluid through a passagewaythrough a radial transducer, the passageway being formed between aninside surface of the radial transducer and the outside of a tubecentrally and axially positioned at least partially through thepassageway.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an apparatus for treating fluidaccording to the present invention;

FIG. 2 is an end view of a fluid passageway through the apparatus ofFIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the discussion of the Figures the same numbers will be usedthroughout to refer to the same or similar components.

In FIG. 1 an apparatus 10 according to the present invention is shown.The apparatus comprises a radial transducer 12 which is connected to apower supply 14 and encloses a passageway 16 axially positioned throughthe radial transducer. The passageway and transducer are symmetricallypositioned around an axis 24. Axial transducer 12 is positioned for flowthrough passageway 16 by a pair of flanges 18 as shown. These flangesmay be of any suitable construction and may be joined to transducer 12by any suitable means. The transducer is joined to flanges 18 sealinglyfor the flow of fluids through a passage inlet 36 to a passage outlet 38as shown by arrows 40.

Transducer 12 can be of any suitable configuration for providingultrasonic power into passageway 16. For instance, prefabricated radialtransducers are available at a variety of frequencies. These transducersare considered to be well known to those skilled in the art and anysuitable configuration may be used so long as ultrasonic power isprovided to passageway 16. Passageway 16 is sized so that the ultrasonicenergy transmitted into passageway 16 is of a wavelength equal to thediameter of passageway 16. A variety of transducer frequencies may beused. Such frequencies may vary from about 10 to about 400 kilohertzwith frequencies from 20 to about 200 kilohertz being preferred.

As shown in FIG. 1 a tube 20 is positioned coaxially in axial transducer12 and extending at least partially through passageway 16. The ends 22of tube 20 are desirably closed by any suitable configuration andpreferably with a curved elliptical or otherwise rounded configurationto minimize the restriction of flow created by tube 20. Tube 20, whileit may be open-ended with a gas flow through the tube or otherwisepositioned in the tube, is desirably closed. The closed tube is filledwith any suitable gas which will not transmit ultrasonic energy insidetube 20, tube 20 is desirably supported coaxially with transducer 12 inpassageway 16. A plurality of supports 26 are shown supporting tube 20in position. Adjustable fasteners 28 are positioned to sealingly engageflanges 18 to permit adjustment of tube 20 and retention of tube 20 inpassageway 16. While four support tubes have been shown in FIG. 2 itwill be understood that few more or fewer supports could be used. It ishowever, desirable that the supports be sufficient to maintain tube 20centrally positioned in passageway 16. Preferably at least threesupports are used.

As shown in FIG. 1 fluid flows into passageway 16 via inlet 36 and outvia outlet 38 as shown by arrows 40.

In operation ultrasonic energy is introduced into the fluid inpassageway 16 from an inner surface 30 of passageway 16. The ultrasonicenergy, as well known to those skilled in the art, is transmitted inwaveform and passes inwardly to the inner surface of tube 20. Since tube20 is filled with a non-transmitting fluid the wave energy is reflectedback resulting in intense energy with cavitation and the like in thespace defined by inside 30 of passageway 16 and an outside 32 of tube20. Desirably, axis 24 is positioned at ½ of 1 wavelength at thefrequency of transducer 12 from inside 30 of passageway 16. The distancebetween the inside 30 of passageway 16 and the outside of tube 20 is adistance which is not a multiple, i.e. multiple or fraction, of theultrasonic wavelength at the chosen frequency which will permit astanding wave in passageway 16. The diameter of tube 20 is sufficient toresult in a space less than ½ wavelength between inside 30 of passageway16 and outside 32 of tube 20. This results in intense cavitation normalto the fluid flow in passageway 16. It is important that the distancebetween the inside of passageway 16 and the outside of tube 20 be lessthan a multiple of the wavelength produced by transducer 12 which willresult in a standing wave. Energy transmitted into passageway 16 issufficient to result in severe intense cavitation in the fluid flow withthe intensity increasing toward the center of the radial transducer. Thesealed tube reflects the waves to the originating surface thusincreasing the intensity between the outside 32 of tube 20 and inside30. The intensity between inside 30 of passageway 16 and outside 32 oftube 20 is many times the intensity radiating from the source.

This high intensity creates destructive forces that destroy bacteria orviruses by instant high temperatures of thousands of degrees Celsius andpressures of hundreds to thousands of atmospheres at heating times lessthan a microsecond. While Applicant does not wish to be bound by anytheory it appears that in addition OH and H₂O₂ radicals are formed whichdestroy bacteria and shock waves are also generated which destroycellular structures and bacteria. Bacteria and viruses are organiccompounds and are destroyed in such an environment. Further,non-elemental materials such as nitrates and other undesirablecontaminates are also destroyed. For instance, nitrates may be convertedinto water, nitrogen and oxygen by treatment in the apparatus. Residencetimes in the apparatus are desirably at least about 50 milliseconds.

Desirably, the energy transmitted into passageway 16 at surface 30 isfrom about 1.6 to about 1.8 watts per square centimeter. Typically,under such conditions the energy level at outer surface 32 of inner tube20 is about 9.5 to about 10.0 watts per square centimeter. Desirably,the average energy level in passageway 16 is greater than about 1.5watts per square centimeter. Under these conditions substantially allnon-elemental compounds in the flowing stream are dissociated.

The fluids treatable in the method of the present invention comprise anygas or liquid from which it is desired to remove contaminates. Water isa frequently treated liquid and is readily treated by the method of thepresent invention.

The fluids are treated by the method of the present invention by passingthe fluids through the passageway and passing the ultrasonic energy intothe fluid at the levels discussed above. Desirably, the fluids areretained in the passageway for a time equal to at least about 50milliseconds.

EXAMPLE

A radial transducer having an inner diameter of 3.0625 inches and alength of 6 inches is used with a tube having an outer diameter of 0.500inches and a length of 6 inches. The radial transducer radiatesapproximately 600 watts from its inner surface. At this power level1.611 watts per square centimeter of power is delivered to thepassageway 16. A liquid flow rate of 72 hundred gallons per hour throughthe apparatus was used. At this flow rate the residence time of thefluid in the apparatus is about 93 milliseconds. This treatment systemis effective to destroy all bacteria or viruses contained in the flowingfluid.

Having thus described the invention by reference to certain of its'preferred embodiments it is pointed out that the embodiments describedare illustrative rather than limiting in nature and that many variationsand modification are possible within the scope of the present invention.

1. An apparatus for treating fluids, then apparatus comprising: a) acentral passageway having an inner surface and a central axis forcontaining a fluid; b) a radial ultrasonic transducer being positionedto transmit ultrasonic energy into the central passageway toward thecentral axis; c) a tube adapted to reflect back the transmittedultrasonic energy and having a cylindrical outer surface and coaxiallyand centrally positioned in the central passageway, the outer surface ofthe tube being positioned at a distance from the inner surface of thecentral passageway which is not a multiple of a wave length of thetransmitted ultrasonic energy to reflect back an energy into the centralpassageway from the outer surface of the tube toward the inner surfaceof the central passageway at an intensity greater than that of thetransmitted energy; d) a fluid inlet to the passageway; and e) a fluidoutlet from the passageway.
 2. The apparatus of claim 1 wherein thefluid is a gas.
 3. The apparatus of claim 1 wherein the fluid is aliquid.
 4. The apparatus of claim 1 wherein the tube is a sealed tube.5. The apparatus of claim 1 wherein the tube contains a gas.
 6. Theapparatus of claim 1 wherein the energy transmitted at the inner surfaceof the central passageway into the central passageway is at theintensity from about 1.6 to about 1.8 watts/cm².
 7. The apparatus ofclaim 1 wherein the energy reflected at the outer surface of the tube isat the intensity from about 9.5 to about 10.0 watts/cm².
 8. Theapparatus of claim 1 wherein an average energy in the passageway isgreater than about 1.5 watts/cm².
 9. The apparatus of claim 1 whereinthe central passageway has a diameter equal to one ultrasonic wavelengthat a frequency of the transducer.